Let the default controller function use absolute input

And convert the VisController to use it.
Don't restrict animations to the keyframe time limits
Clear the old text keys when setting new animation sources
Use an unconnected object list for animation sources

We'll want the controllers, as the plan is to use their keyframe controllers
to animate the actual skeleton used for the meshes.
Remove an unneeded function
Fix a couple messages
Update animation source controller targets
Implement a KeyframeController
Don't create a controller for empty keyframe data
Only get the non-accum root's keyframe when updating positions

The actual animation pose is now handled by the controllers, based on the
current animation time.